This application requests support for the Coordinating Center for the multicenter trial of Supplemental Therapeutic Oxygen for Prethreshold Retinopathy of Prematurity (STOP-ROP). The EMMES Corporation staff participated with the Executive Committee in preparing the STOP-ROP Manual of Procedures and research plan which was submitted with the lead application from the University of Rochester. The qualifications of The EMMES Corporation to participate in STOP-ROP as the Coordinating Center are described in terms of personnel, extensive coordinating center experience, facilities, and other resources. The Coordinating Center will assist STOP-ROP in its primary goal to systematically assess the effects of supplemental therapeutic oxygen therapy on the development of Threshold (severe) ROP in 880 infants enrolled with Prethreshold (moderate) ROP from 20 to 30 Study Centers. Infants with Prethreshold ROP in at least one eye will be randomized to receive conventional versus supplemental therapeutic oxygen for at least two weeks. Each infant will be followed until he or she reaches 3 months after the expected date of full term delivery. Infants' rate of growth, pulmonary status, ophthalmic status, and length of hospital stays will be prospectively measured and analyzed. Participating Study Centers will adhere to common definitions, eligibility criteria, diagnostic and treatment procedures, methods of measurement, quality control, and administrative policies as specified in the STOP-ROP Manual of Procedures. The Coordinating Center will collect, process, and analyze study data and coordinate study activities. A Data and Safety Monitoring Committee (DSMC) will review all data and supervise the conduct of the study.